Shoppers look at products at the Upper West Side Apple Inc. store in New York, U.S., on Sunday, July 20, 2014. Apple Inc. is expected to release earnings data on July 22. Photographer: Michael Nagle/Bloomberg

Often criticized for its lagging workforce diversity, Silicon Valley appears to be feeling the pressure. Over the past three months, a half-dozen leading tech companies have released diversity numbers, accompanied by pledges to improve them. Still others have promised to follow suit.

But one set of statistics has been noticeably absent: the age of those companies' workers.

Silicon Valley's conversation about diversity has revolved chiefly around gender and race, although the stereotype of the techie as white, male and young has written out the over-40 set as well.

The Chronicle requested employees' age data from the seven tech companies that have recently released diversity reports: Google, Pinterest, Salesforce, Twitter, Yahoo, Facebook and LinkedIn. All either declined to provide the information or did not respond to the request.

Requests for diversity data were also made to more than a dozen additional companies. Only one, Hewlett-Packard, shared information related to workforce age, which it has published in an annual report since 2001. At HP, a quarter of its U.S. employees are 30 or younger, more than half are between 31 and 50 and about 18 percent are over 51.

Several companies noted that the numbers they released publicly were the same numbers that they are required to report to the U.S. Equal Employment Opportunity Commission. And though the commission is responsible for enforcing laws against workforce discrimination, including age discrimination, the rules requiring companies to report diversity breakdowns to the government are tied specifically to the Civil Rights Act of 1964, which does not cover age.

Data not tracked

Age discrimination is prohibited in California by both the federal Age Discrimination in Employment Act of 1967 and the California Fair Employment and Housing Act. But the government doesn't track age diversity in the workplace.

"Tech companies should be releasing descriptions of their workforce in all dimensions," she said. "Age is one very important demographic that signals whether or not a company has an inclusive culture. It's important alongside race, gender and sexual orientation."

A first step

The loud push for Silicon Valley companies to make public their federally reported diversity data stems from a hope that disclosing such information is a first step toward valley employers changing their ways.

Silicon Valley's mantra has long been that tech is a meritocracy, but the numbers belie that. There are few qualified minority and female technology experts to begin with, but often the tech world has not welcomed those who manage to get in.

Though there are plenty of visible people over 40 in top tech jobs (most of them men), there have also been several age discrimination lawsuits against major companies, and frequent reports of employers and funders passing on older workers in favor of younger ones.

Valley mythology

The young hoodie-clad startup founder is deeply embedded in Silicon Valley mythology. On websites like Quora, queries such as "If you are 30, are you too old to start a company?" are common. And without the data, it's hard to tell how much of a problem age discrimination is.

Last year, PayScale reported that of 32 tech companies it surveyed, just six had a workforce with a median age greater than 35. Most of those were older, more established companies such as IBM and Dell. The Chronicle queried companies this year about the median age of their employees, and only two provided answers: Autodesk and Cisco, whose median ages are 40 and 40 1/2.

This week, The Chronicle also requested diversity data from HP, Adobe, Apple, eBay, Pandora, Square, Dropbox, Zendesk, Tesla, Oracle, Intel and Netflix. EBay said it would release numbers soon, but that they would not include age. Pandora and Apple also said they will release them, though they would not specify what the content will include. Adobe publishes its gender number annually, but declined to provide anything more.

No data

Square, Dropbox, Zendesk, Tesla and Oracle declined to provide any data. Intel and Netflix did not respond.

Lazowska, the University of Washington computer scientist, said that Google deserves much credit for being the first company to publish its data.

But he underscored the importance of including age as a measure of diversity - and the value that diversity brings to the workplace.

"You don't need to believe in these things in order to believe in the value of diversity - all you need to do is want the best possible product," he said.